Research into the mechanism and etiology of hypertension has demonstrated both structural and functional changes in the artery walls of hypertensive animals and patients. This study will explore the physiologic basis and significance of functional changes in vascular smooth muscle associated with DOCA-hypertension in rats. We will lower the blood pressure in one leg of a rat by constricting the major artery supplying the leg. Having protected one leg from high pressure, DOCA-hypertension will be induced in these rats. We will study in vitro the isometric contractile responses of helically cut strips of femoral artery from the protected and unprotected legs of the hypertensive rats and their normotensive controls to determine whether or not the decreased maximum force generating capacity of strips from the arteries of hypertensive rats is a secondary adaptation to high pressure. Histometric and strip studies will determine the orientation of smooth muscle in the artery wall and whether changes in smooth muscle orientation are responsible for decreased contractility. Direct stimulation of the contractile protein machinery (bypassing the membrane phase of contraction) of smooth muscle of helical-strips of femoral artery of DOCA-hypertensive rats with a calcium ionophore will enable us to better define whether decreased contractility and increased excitability of arterial strips associated with hypertension are the results of changes in membrane excitation, excitation-contraction coupling, or the contractile protein machinery.